1. Field of the Invention
The invention relates to a driving circuit, and more particularly to a driving circuit with power metal-oxide-semiconductor (MOS) breakdown protection.
2. Description of the Related Art
FIG. 1 shows an H-bridge output stage of a driving circuit. Referring to FIG. 1, the H-bridge output stage is coupled between an operation voltage source VDD and a ground GND and used to drive a load 10 coupled between output nodes OUT10 and OUT11, such as an inductance element. The H-bridge output stage comprises four output-stage elements that are P-type metal-oxide-semiconductor (PMOS) transistors P10 and P11 and NMOS transistors N10 and N11. As known by the one skilled in the art, when the PMOS transistor P10 and the NMOS transistor N11 are turned on while the PMOS transistor P11 and the NMOS transistor N10 are turned off, a current path passing through the PMOS transistor P10, the inductance element 10, and the NMOS transistor N11 is formed to drive the inductance element 10. When the PMOS transistor P11 and the NMOS transistor N10 are turned on while the PMOS transistor P10 and the NMOS transistor N11 are turned off, a current path passing through the PMOS transistor P11, the inductance element 10, and the NMOS transistor N10 is formed to drive the inductance element 10. In this structure, when a current from the inductance element 10 flows to one of the output nodes OUT10 and OUT11 of the H-bridge output stage, the corresponding NMOS transistor may be burned.
For example, when the PMOS transistor P10 and the NMOS transistor N11 are turned on, the current from the inductance element 10 flows to the output node OUT 11. In this case, the current from the inductance element 10 may flow to the body of the NMOS transistor N11 at the time when the NMOS transistor N11 is turned off, which may trigger the parasitical NPN of the NMOS transistor N11 to be turned on, resulting in the breakdown of the NMOS transistor N11. After the NMOS transistor N11 is broken down, the NMOS transistor N11 operates as a voltage source with a holding voltage. When the PMOS transistor P11 is turned on and the holding voltage is less than the voltage of the operation voltage source VDD, the NMOS transistor N11 is burned, and the H-bridge output stage can not work any more.
Thus, it is desired to provide a drive circuit which provides power NMOS breakdown protection.